Heating oil processing for improved quality



H- A. RICARDS, JR., ET AL 2,7 7,856

Sept. 13, 1955 HEATING OIL PROCESSING FOR IMPROVED QUALITY Filed July 9,1952 2 Sheets-Sheet l L0 E! I I mw mm -m a T aw nww. E 3 +1 I All J OW 5I on I a w 3 \TM mm v 45 wzrzmz 21 3.5 I vm o 1 v mm 5m m mm 3 T I A wQcusrnond L. Butts Harold A.Qi.ards Jngbmveotors Hqrrzs m. Hqr'bzband,

Sept? 13, 1955 H. A. RICARDS, JR, ET AL 2,717,856

HEATING OIL PROCESSING FOR IMPROVED QUALITY Filed July 9, 1952 O 2Sheets-Sheet 2 I own c o WJE N .4 C o E U 103 0 2: 0 2. '3 9 b 0 011 v Pg g 8 6 0: U'u u Q 2 a H MO: 0 S 0 Q :1 I 1 5 2 32 t: 6". (.L LUU o Q 0:0 U

S: O L.

o 2 3 3 O o O O arbon Qesidue (1o bottoms) mgmond L.b ett Harold A. Q1Cards Jr. Hat-r15 m. Hqrt'zband brzverztors CLtooraec United StatesPatent HEATING OIL PROCESSING FOR IlVlPROVED QUALITY Application July 9,1952, Serial No. 297,832 3 Claims. (Cl. 196-29) The present invention isconcerned with an improved process for the production of high qualityheating oil blends comprising virgin and cracked constituents. Theinvention is more particularly directed to a process for the handling ofthe virgin constituents and the cracked constituents whereby therespective constituents may be effectively blended to produce asatisfactory high quality blended heating oil product. In accordancewith the present. invention, a stable heating oilof low Conradsoncarbon-residue content is produced from virgin and catalytically crackedheating oil constituents by promptly caustic washing the catalyticallycracked constituents before exposure to oxygen, and by partiallyair-sweetening the sour virgin constituents to a predetermined coppernumber. The heating oil product of the present invention has anexcellent odor, burning quality and storage stability.

.The present invention is broadly concerned with the production ofimproved hydrocarbon mixtures known as, heating oils, of the natureemployed in various burner systems, as diesel fuels, or as domestic andindustrial heating oils. Heating oils may be derived from petroleum by avariety of methods including straight distillation from crude petroleumoil, and thermal or catalytic cracking of various petroleum oilfractions. Heretofore, in the art, heating oil blends comprised arelatively large proportion of virgin heating oil as compared to crackedheating oils. However, due to the desirability of virgin heating oils asfeed stocks to various cracking operations, as for example, a fluidcatalytic cracking operation, the average blends now comprise anincreasing proportion of cracked heating oil fractions as compared tovirgin stocks.

It is known in the art that heating oils consisting com pletely or inpart of catalytic cracked stocks are characterized by an undesirableinstability giving rise to the formation of sediment. It is also knownthat when cracked heating oils are blended with virgin heating oilscompletely sweetened by conversion type processes (processes whichaccomplish sweetening by oxidation of mercaptans to other sulfur formssuch as disulfides), certain undesirable characteristics are increaseddue to the incompatibility of the components. As a result, such blendedfuel oils comprising cracked constituents and virgin constituents, tendto cause clogging of filters, orifices, or conduits associated with theburning systems in which they are employed.

It is also known in the art that when certain virgin heating oils areblended with a cracked heating oil, the carbon residue of the blend inmany cases exceeds the carbon residue of either the virgin heating oilor the cracked heating oil. This carbon residue is an indication of theextent the blended heating oil will carbonize the burners, particularlya rotary burner of the wall flame type in actual use, and to some extentdetermines the burning characteristics and desirability of the fuel.

. In order to improve the quality of blended heating oils, A

various processes have been practiced in the art. It is Carbon residueresiduum) is obtained by subjecting a sample of the heating oil to anASTM distillation, taking the 10% bottoms from the distillation andsubjecting-1t to a test for Conradson carbon.

2,717,856 Patented Sept. 13, 1955 known in the art to process a virginheating oil by a caustic wash if the oil be relatively sweet. On theother hand, if the virgin heating oil has a relatively high mercaptancontent so as to render it sour, the oil is normallyprocessed by adoctor treat or an equivalent sweetening voperation. On the other hand,light cracked heating oils in many operations merely require a causticwash. However, the conventional procedure is to secure the crackedheating oil from a relatively severe cracking operation in which case itis necessary to acid treat the crackedheating oil followed by a causticwash in order to control the carbon residue. This latter operation isnot desirable since acid treatment polymerizes' many desirableconstituents resulting in a loss in yield. Furthermore, the sludgeresulting from such acid treating is expensive and ditiicult to handle.a

In accordance with the present invention a stable heating oil blend oflow Conradson carbon residue (10% residuum) and improved storagestability isproduced by carefully controlling the sweetening of the sourvirgin fraction (or any combination of sour virgin and crackedcomponents) to a predetermined degree, and by promptly caustic washingthe catalytically cracked component. The

finishing procedure for the catalytic component is not limited to promptcaustic washing. More severe treating such as acid may be employed,however, such severe treating of the catalytic component can beminimized or eliminated by virtue of the improved processing of the sourcomponents. I

Heating oils which may be prepared by the present process arehydrocarbon mixtures containing virgin oils, and more than about 10%,preferably from about- 15% "to 60%, by volume of stocks derived fromcracking operations. More precisely still, the finished blends maybecharacterized as petroleum fractions containing a virgin stock sweetenedto a predetermined degree and a proportion of cracked stocks greaterthan 10%, preferably from about 15% to 60% by volume, and falling withinA. S. T. M. specification D396-48T for Fuel Oils (Grades No. l or 2).Inspections of a typical heating oil blend are for example:

Gravity, A. P. I t 34.5 Distillation, A. S. T. M.: 1

Initial, B. P. F 363 10% at F 438 50% at F 504 at F 583 Final, B. P. F640 Flash, F 158 Color, Tag Robinson 15 Viscosity, S. S. U./ 34.7 Pourpoint, F 0 Sulfur, wt. per cent .37 Suspended sediment, mgs./100 ml 1.0Carbon residue on 10% residuum, percent 0.8 Corrosion, 1 hr. at 212 FPass Diesel index 48.2 Aniline point, F

The process of the present invention may be more fully understood byreference to Fig. 1 of the drawing illustrating one embodiment of thesame. Referring specifically to the drawing, a crude oil feed stock isintroduced into distillation zone 1 by means of line 2. Temperature andpressure conditions in zone 1 are adapted to remove overhead by means ofline 3 normally gaseous'hydrocarbons and to remove by means of line 4hydrocarbon constituents boiling in the motor fuel and naphtha boilingranges. A virgin heating oil fraction is removed from zone 1 by means ofline 5 while agas oil fraction isremoved by means of line 6. A residuumfraction comprising the higher boiling constituents is removed as abottoms by means of line 7. The virgin heating oil frac'- tion removedby means .of line.5 may betreated by various processes in order torefine the same. However, in accordance with the present invention thisfraction is sweetened a predetermined degree. Any process capable ofcontrolled sweetening may be used, as for example aircaustic,hypochlorite, etc. As an-example,'the air-caustic process is typical andis most easily adapted to partial sweetening. The heating oil isintroduced into an initial caustic treating zone 50 wherein the same iscontacted "with caustic introduced by means of line 51 and withdrawn bymeans of line 52. This contacting may also be accomplished by means of aline wash rather than in a separate vessel. While the amount of causticmay vary appreciably, it is preferably in the range from about .2 to 1%,preferably about 0.5% by volume based upon the oil. Thestrength ofthe-caustic is in the range from about -12 to '20 B., preferably aboutB. Too high a caustic strength may remove some natural promotors ofsweetening, while too low a caustic strength may not remove enough ofthe acidic materials which cause emulsions and processing difiiculties.The oil is withdrawn fromzone by-means of line 53 and passed intosweetening "zone 54 wherein the same is mixed with stronger causticintroduced by means of line 55. Spent caustic is withdrawn by means ofline 56. The amount of caustic used may be in the range from about 1 to10% by volume based upon the oil. A preferred quantity is about 2-3% byvolume. The strength of the caustic may range from about 40 B. to 55 B.but is preferably from about 48 to 52 B. In accordance with the presentinvention air or another oxygen containing gas is passed into zone 54 bymeans of line 57. During the addition of the air the mixture isvigorously agitated. This operation may take place at a temperature inthe range of 80150 F., preferably at l20l25 F. The use of highertemperatures islimited'by the color degradation which can be tolerated.The treated oil, sweetened to a predetermined level is then water washedand is withdrawn from zone 54 by means of 'line 58 and blended withcracked heating oil constituents secured as hereinafter described.

It is to be understood that distillation zone 1, treating zones 50 and54, may comprise any suitable number and arrangement of stages. The gasoil fraction removed by means of line 6 is passed to cracking zone 16which may .comprise any suitable cracking operation, as for example, athermal or a catalytic cracking process. However, the present inventionis particularly directed toward the production of a high qualityvirgin-cracked heating oil blend wherein the cracking process comprisesa catalytic crack- =ing operation, as for example a fiuid catalyticcracking :operation.

.A fluid catalytic cracking tsections: cracking, regeneration, andfractionation. The cracking reaction takes place continuously in onereactor :at a temperature in the range from about 800 F. to 1050 F. Thespent catalyst is removed continuously for re- ;generation in a separatevessel, from which it .is returned fto the cracking vessel, which is ata pressure below about .200 lbs. usually below about 50 lbs. per sq. in.Continuity of flow of catalysts as well as of oil is thus accomplished,and the characteristic features of fixed-bed designs involving theintermittent shifting of reactors through cracking, .purging, andregeneration cycles are eliminated.

Regenerated catalyst is withdrawn from the regenerator and flows "bygravity down a standpipe, wherein a su'f- 'ficiently high pressure headis built up on the catalyst to allow its injection into the fresh liquidoil stream. The resulting mixtureof oil and catalyst flows into thereaction vessel, in which gas velocity is intentionally low, so that ahigh concentration of catalyst will result. The

plant is composed of three cracking that takesplace results in carbondeposition on the catalyst,rcquiring regeneration of the catalyst. Thecracked .product oil vapors are withdrawn from sthe top of the tre'actorafter passing through cyclone separators .to

: stituents and to remove by free them of .any entrained catalystparticles, while the spent catalyst is withdrawn from the bottom of thereactor and is injected into a stream of undiluted air which carries thecatalyst into the regeneration vessel. The products of combustionresulting from the regeneration of the catalyst leave the top of thisvessel and pass through a series of cyclones where the bulk of theentrained catalyst is recovered. The regenerated catalyst is withdrawnfrom the bottom of the vessel to complete its cycle.

The cracked products are removed from cracking zone '16 (overhead fromthe reactor) by means of line 28 and introduced into a distillation zone29. Temperature and pressure conditions in zone 29 are adjusted to.remove overhead by means of line 30 normally gaseous conmeans of'line31 hydrocarbon constituents boiling in the motor fuel boiling range. Afraction boiling above the heating oil boiling range is removed as abottoms fraction by means of line 32. A fraction boiling in the heatingoil boiling range is removed by means of line 33 and in accordance withthe present invention is promptly treated in zone 21. The fresh causticor other treating agent is introduced by means of line 22 while thespent treatingagent is removed by means of line 23. The cracked heatingoil is removed from this finishing zone by means of line 27 and blendedas hereinbefore described with a virgin heating oil in line 58.

The present invention is broadly concerned with the production ofheating oils comprising virgin and cracked constituents and having goodcarbon residue characteristics'and a high stability, particularly withrespect to sediment formation. As is known, domestic heating oils mustmeet certain odor requirements to be acceptable to the customer. Inorder to produce finished oils with satisfactory odor, the sour virgincomponent must be sweetened. This sweetening can be accomplished eitherby conversion or extractive methods.

Various operations have demonstrated that complete conversion sweetening(to doctor pass) causes excessive product quality degradation of thevirgin oil and increased incompatibility when this oil is blended withuntreated or caustic washed catalytic components. However, it has beendiscovered that partial conversion sweetening within rather narrowlimits will minimize this degradation of the virgin constituents andstill yield a heating oil product having acceptable odor.

The process of the present invention may be more fully understood by thefollowing example illustrating the same:

Example Various operations were utilized for sweetening two virgin feedstocks having approximately an copper number? The results of these testsas measured by change of carbon residue (10% bottoms) with degree ofsweetening are presented graphically in Figure 2. It is to be observedthat at first, there is a gradual increase in carbon residue from about0.04 to 0.06 as the sweetening progresses from 80 to 1520 copper number.Further sweetening below 15 copper number causes an unexpected and veryrapid increase in carbon residue to 0.11 wt. per cent at completesweetening. Similar trends were observed with respect to sedimentforming characteristics of the sweetened oils.

Since the virgin heating oils are blended with catalytic components, thebehavior of the partially sweetenend oils in blend with promptly causticwashed catalytic oils 'was determined. The carbon residue (10% bottoms)and accelerated storage data presented .below are for equivolume blendsof the virgin oil with a promptly caustic washed 630 FEP catalyticstock. It is evident that as the degree of sweetening increases,incompatibility of the virgin component with the catalytic stock alsoincreases, as shown by the difierence between experimental and cal- 3Copper number-is "equivalent to *mg. 015 mercaptan 'sulfur per cc. ofgasoline.

Copper Number of Virgin Oil Copper Number of Blend 8 MMM ExperimentalCarbon Residue (10% Bottoms), Wt. percent 0. Calculated Carbon Residue(10% Bottoms) 0. Experimental minus Calculated Values, Wt.

percent Sediment Formation in Storage, mg./l n11.

I Equivolume mixtures of the caustic washed catalytic oil.

b Assuming linear blending.

Ill-weeks storage at 125 F.

d Passes doctor test.

virgin oil with a 630 FEP promptly From the above it is apparent thatthe mercaptan-containing virgin heating oil fraction should be sweetenedto a copper number in the range from about 15-30, prefer ably to acopper number What is claimed is:

1. Improved process for the production of a heating oil blend from amercaptan-containing virgin fraction and from a catalytically crackedfraction which comprises caustic washing the cracked fraction prior tocontact with air, partially sweetening the virgin fraction to a coppernumber in the range from about 15 to 30 and blending the respectivefractions.

2. Improved process for the production of a heating oil blend whichcomprises segregating a virgin heating oil fraction and a gas oilfraction in a distillation zone, cracking said gas oil to produce lowerboiling hydrocarbons, segregating a cracked heating oil fraction fromthe cracked product, promptly caustic washing the cracked fractionvirgin fractions.

3. Process as defined by claim 2 wherein the virgin fraction issweetened to a copper number in the range from about 17-23.

in the range from about 17-23.

References Cited in the file of this patent UNITED STATES PATENTS

1. IMPROVED PROCESS FOR THE PRODUCTION OF A HEATING OIL BLEND FROM AMERCAPTAN-CONTAINING VIRGIN FRACTION AND FROM A CATALYTICALLY CRACKEDFRACTION WHICH COMPRISES CAUSTIC WASHING THE CRACKED FRACTION PRIOR TOCONTACT WITH AIR, PARTIALLY SWEETENING THE VIRGIN FRACTION TO A COPPERNUMBER IN THE RANGE FROM ABOUT 15 TO 30 AND BLENDING THE RESPECTIVEFRACTIONS.